There has been proposed the method for forming color images on a thermal transfer image-receiving sheet which is dyeable with a sublimation dye by using a thermal transfer sheet composed of the sublimation dye as a recording agent and a substrate on which the sublimation dye is supported. In this method, the dye is heated using a thermal head of a printer as a heating means and transferred on the image-receiving sheet to obtain the color images. The thus formed images are very clear and excellent in transparency because of the dye used, and are therefore expected to provide high-quality images which are excellent in reproducibility of half tones and gradation. For this reason, thermal transfer image-receiving sheets capable of exhibiting the above properties have been developed.
Patent Document 1 discloses a heat-sensitive transfer image-receiving sheet including a substrate, and at least one receiving layer containing a polymer latex and at least one heat-insulating layer containing a hollow polymer which layers are formed on the substrate wherein the polymer latex contained in the receiving layer is composed of two or more kinds of dyeable polymers which are different in glass transition temperature from each other, for the purpose of improving an image density and defects of images.
Patent Document 2 discloses a coloring matter receiving material for thermal sublimation printing which includes a coloring matter receiving layer containing a graft polymer composed of an unsaturated copolyester as a main chain and a vinyl copolymer as a side chain, and a substrate, for the purpose of improving color density, stability of images, and the like.
Patent Document 3 discloses a polyester-based resin containing, as a main component, a graft polymer product having a tan δ peak temperature of 40° C. or higher and a glass transition temperature of 15° C. or higher, and a molecular weight of from 0.15 to 1.5 in terms of a reduced viscosity which is in the form of a polymer composed of an unsaturated bond-containing polyester as a main chain and a radical polymerizable unsaturated monomer as a side chain, and a sublimation transfer image receptor having a dyeable layer composed mainly of a dyeable resin containing the polyester-based resin, for the purpose of improving a dyeing sensitivity, and a durability and storage stability of images.
Patent Document 4 discloses a thermal transfer image-receiving material including a substrate and at least one image-receiving layer formed on the substrate which receives a coloring matter transferred from a thermal transfer coloring matter donating material upon heating to form an image thereon and which is formed of a composition prepared by dispersing a coloring matter receiving substance in a water-soluble binder, wherein an uppermost layer of image-receiving surface-forming layers in the image-receiving material contains a co-dispersed material composed of a silicone compound and a plasticizer having an [organic/inorganic] ratio of 1.5 or more, for the purpose of improving film properties and a transferred image density.
Patent Document 5 discloses a receiving layer composition for thermal transfer image-receiving sheets which includes a resin containing a polyester obtained by polycondensing an alcohol component containing an alkyleneoxide adduct of bisphenol A in an amount of 50 mol % or more and a carboxylic acid component containing an alicyclic carboxylic acid in an amount of more than 50 mol %, and a polyether-modified silicone having an oxyethylene group and/or an oxypropylene group, for the purpose of improving dyeability and releasability.    Patent Document 1: JP-A 2007-229987    Patent Document 2: JP-A 4-319489    Patent Document 3: JP-A 10-60063    Patent Document 4: JP-A 3-101993    Patent Document 5: JP-A 2009-262337